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    <meta charset="UTF-8" />
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    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <script>
      // var arr = [{ name: 'shanghai' }, { name: 'chengdu' }, { name: 'beijing' }]
      // var x = arr.map((item) => item.name)
      // console.log(x)

      var arr = [
        {
          id: 1,
          count: 2
        },
        {
          id: 2,
          count: 2
        },
        {
          id: 3,
          count: 2
        },
        {
          id: 4,
          count: 2
        }
      ]
      let c = 4
      arr.forEach((item) => (c += item.count))
      console.log(c)
    </script>
  </body>
</html>
